Adhesion promotion of cyanide-free white bronze

Abstract

White bronze is electroplated from a cyanide-free tin/copper bath onto a void inhibiting layer coating a copper underlayer. The void inhibiting metal layer includes one or more void inhibiting metals.

What is claimed is: 
     
       1. A method comprising:
 a) depositing onto a substrate comprising a copper containing layer a metal layer composed of zinc or a binary zinc/copper alloy adjacent the copper containing layer; 
 b) drying the substrate with compressed air before heating for 0.5 to 2 hours at a temperature from 100° C. to 200° C. to form a brass layer; and 
 c) electroplating a tin/copper alloy layer from a cyanide-free tin/copper electroplating bath adjacent the brass layer. 
 
     
     
       2. The method of  claim 1 , wherein the metal layer of zinc or binary zinc/copper alloy is at least 0.02 μm thick. 
     
     
       3. The method of  claim 2 , wherein the metal layer of zinc or binary zinc/copper has a thickness of 0.05 μm to 10 μm. 
     
     
       4. The method of  claim 1 , wherein the tin/copper layer is at least 0.01 μm to 20 μm thick. 
     
     
       5. The method of  claim 1 , wherein the binary zinc/copper alloy comprises 10% to 90% zinc. 
     
     
       6. The method of  claim 1 , wherein the brass layer comprises 80% to 64% copper and 20% to 36% zinc.